High-$Q$ 4–6-GHz Suspended Stripline RF MEMS Tunable Filter With Bandwidth Control

摘要

This paper presents a high-$Q$ two-pole tunable filter with frequency and bandwidth control. The filter is implemented using suspended-stripline ring resonators and planar RF microelectromechanical systems capacitive networks. A tuning range of 3.7–5.95 GHz with an absolute 1-dB bandwidth of ${hbox {110}}pm {hbox {20}}~{hbox {MHz}}$ (3.6%–1.7% fractional bandwidth) is first demonstrated with an insertion loss $< {hbox {2.5}}~{hbox {dB}}$ . The bandwidth can be controlled at any frequency, and a 1-dB bandwidth of 90–515 MHz is also demonstrated at 5.5 GHz. The measured ${ Q}_{ u}$ is 115–250 at 3.7–5.95 GHz. The measured third-order intermodulation intercept point and 1-dB power compression point are $> {hbox{35 dBm}}~(Delta { f} = 300~{hbox{kHz}})$ and 20 dBm, respectively. To our knowledge, this filter represents the state-of-the-art in tuning performance and $Q$ for planar designs at 2–6 GHz.